This invention is generally related to vibration devices. Applications include devices such as those that produce haptic sensations to enhance the realism of a video game, vibratory parts feeders, and vibration shakers.
Actuators that provide force feedback and haptic sensations are used for a wide range of applications including gaming devices, medical simulators, and flight simulators. Actuators in haptic devices create force sensations which are felt by the user.
One method for generating a haptic sensation is to use vibratory actuators such as those described in U.S. Pat. Nos. 6,275,213 and 6,424,333. Vibratory actuators provide a low cost method for generating force sensations, and multiple vibratory actuators can used to generate a range of sensations. In many existing devices vibrations are generated through rotary motors with an eccentric mass.
A limitation of eccentric mass rotary vibrators is that under continuous vibration the force of vibration is coupled to the magnitude of vibration, and thus it is not possible to modify the magnitude of vibration for a given vibration frequency. Another limitation of existing vibration devices is that the direction of vibration force is set by the orientation of the vibration actuators, and cannot be modified during operation.
In existing devices there is minimal or no directional information is provided to the user, and the force sensations are limited to the frequency of vibration of the actuators. In existing vibration devices with multiple vibration actuators, there is typically no synchronization of the vibration waveforms of the various actuators, and the phase difference between the different vibrations is not explicitly specified or controlled. This lack of synchronization limits the types of force effects that existing vibration devices can generate.
One application of vibration devices is in haptic input devices such as game controllers. Haptic devices use force to convey information to the user. In computer games and other applications it is desirable to convey a wide range of information to the user through force including frequency, magnitude, and direction of force. Since existing vibration devices do not convey all such information, there is a need to provide increased range of force sensations using vibratory actuators.
Existing tactile vibration devices often use small motors. These motors exert a low magnitude of force, and often require a number of vibration cycles before they build up sufficient force magnitude to be felt. Thus, many existing vibration devices provide tactile sensations that can only be felt at high frequency vibrations, where vibration energy can be built up over time. However, it may be desirable to also generate low frequency sensations to correspond to events that occur at a lower frequency than the vibration frequency. Thus there is a need to generate low frequency force sensations will small actuators.